This invention pertains to printers and more particularly indicating when a print head assemblage which is moving longitudinally parallel to a record medium is to strike the record medium.
Most printers with longitudinally moving print heads are carefully positioned for each print step so that a nearly perfectly registered copy is obtained. Such printers because of their step to step operation or precise positioning are relatively slow operating or require complicated servo systems.
In order to minimize these problems there have been proposed on-the-fly printers wherein at every instant the position of the print head is known. Such printers require complex speed control systems or complex position indicating systems. The latter class of systems fall under two types. Those utilizing magnetic position sensing are represented by U.S. Pat. Nos. 4,082,944; 4,044,881; 3,858,702; and 3,434,581. Those utilizing optical position sensing are represented by U.S. Pat. Nos. 4,076,111 and 3,882,988. Neither of these types satisfy the need for a simple, inexpensive highly precise and very reliable position indicating system.